Sequence representation as an early step in the evolution of language
Fig 3
Performance of Depth-ℓ and trace representations of stimulus sequences in environments that vary in the temporal distribution of information.
The number of stimuli (including informative and uninformative stimuli) is 66 in all environments. The trace decay rate θ = 0.5. The x-axis represents the time-steps or learning opportunities and the y-axis represents the performance measured after a given number of time-steps, as described in the methods section. a: Examples of environments in which productive decisions depend on the last stimulus only (top) or on the last two stimuli (bottom). ✲ indicates uninformative stimuli selected at random for each pattern; ● and ◯ indicate stimuli whose identity determines the correct output. 1 and 0 indicate whether a response is productive or not. b: Learning in an environment of 32 sequences in which only the last stimulus is informative. c: Learning in an environment of 32 sequences in which all four temporal positions are equally likely to be informative. d: Learning in an environment of 32 sequences in which only the first of the four temporal positions is informative.